In a conventional robot control system, a robot control device for controlling a robot and a portable operating device performing operations for teaching the robot are electrically connected to each other via a connection cable. The connection cable transmits teaching data or setting data for teaching the robot from the portable operating device to the robot control device. The connection cable also transmits display data from the robot control device to the portable operating device so that the display data is displayed on a display of the potable operating device.
The connection cable is dragged around by the operator who carries the portable operating device when the operator teaches the robot. The connection cable thus may hamper operation by the operator. To solve this problem, as disclosed in, for example, Patent Document 1, wireless communication between a portable operating device and a robot control device has been proposed to facilitate robot operation.
As illustrated in FIG. 3, a robot control system 51 includes a robot R, a portable operating device TP, and a robot control device RC for controlling operation of the robot R. The robot R performs arc welding and spot welding. The portable operating device TP is used by an operator 53 to perform robot teaching. The portable operating device TP and the robot control device RC wirelessly communicate with each other.
The portable operating device TP includes a display section 41 for displaying teaching data, a keyboard 42 through which the teaching data is entered, and an emergency stop switch 43 for causing an emergency stop of the robot R. The portable operating device TP also has a secondary battery serving as a drive source. The teaching data entered through the keyboard 42 is transmitted to the robot control device RC through wireless communication and stored by the robot control device RC. The robot R has a wrist portion having a distal end to which a work tool such as an arc welding torch or a spot welding gun is attached. Typically, the robot R is installed in the space surrounded by a safety fence 52. The robot control device RC automatically operates the robot R based on the entered teaching data. A connection cable 54 electrically connects the robot control device RC and the portable operating device TP to each other when the robot R is in automatic operation. The connection cable 54 is detachably attachable to the portable operating device TP through a connector (not shown). When the portable operating device TP is electrically connected to the connection cable 54, the secondary battery mounted in the portable operating device TP is charged.
With reference to FIG. 4, the portable operating device TP generates transmission data including the teaching data entered by the operator. The portable operating device TP transmits the transmission data to the robot control device RC through a transmission section 72. The robot control device RC receives the data provided by the portable operating device TP through a receiving section 62 as reception data. The robot control device RC transmits transmission data such as display data to the portable operating device TP through a transmitting section 61. The portable operating device TP receives the data provided by the robot control device RC through a receiving section 71 as reception data.
When the emergency stop switch 43 of the portable operating device TP is pressed, the portable operating device TP transmits data indicating that the emergency stop switch 43 has been pressed to the robot control device RC through a transmission section 72. Based on the data sent from the portable operating device TP, the robot control device RC causes an emergency stop of the robot R. In other cases, the robot control device RC causes the emergency stop of the robot R when wireless communication is temporarily interrupted due to noise or insufficient radio field intensity.
The robot control system disclosed in Patent Document 1 further includes detection means (not shown). The detection means detects whether the electrical connection between the portable operating device TP and the robot control device RC through the connection cable 54 is not established. When the robot R is in automatic operation and the detection means detects that the aforementioned electric connection is not established, the robot control system activates an alarm. This prevents interruption of communication between the portable operating device TP and the robot control device RC due to insufficient charging of the secondary battery, which leads to an emergency stop of the robot R and thus interruption of the production line. Further, when the electric connection between the portable operating device TP and the robot control device RC is not established, the robot control system performs wireless communication between the portable operating device TP and the robot control device RC.
As has been described, when automatic robot operation is being carried out and it is detected that the electric connection between the portable operating device and the robot control device is not established, the robot control system disclosed in Patent Document 1 activates an alarm to warn the operator. This prevents an emergency stop of the robot due to insufficient charging of the secondary battery of the portable operating device. Further, even when the aforementioned electric connection is not established, the robot control system disclosed in Patent Document 1 performs wireless communication between the portable operating device TP and the robot control device RC. The automatic operation of the robot R is thus continued even without connecting the portable operating device to the connection cable to charge the secondary battery in accordance with the alarm. However, if the automatic operation of the robot R is continuously performed despite the alarm, the charging amount of the secondary battery of the portable operating device TP decreases as the time elapses. In this case, eventually, an emergency stop signal is generated to stop the production line.
Accordingly, when an alarm is activated, the portable operating device must be connected to the robot control device. Such a connecting operation is troublesome for the operator. Further, the portable operating device is necessary mainly for robot teaching but unnecessary for the automatic operation of the robot. Specifically, in the automatic operation of the robot, it is desirable to switch to wire communication to eliminate the influence of noise or to continue the automatic operation of the robot with the portable operating device disconnected from the robot control system. Further, a portable operating device performing wireless communication has an advantage in that a plurality of robot control systems may be operated through a single portable operating device. However, when a single robot control device has to be connected to a single portable operating device, as in the case of the robot control system disclosed in Patent Document 1, the portable operating device cannot be used to operate other robot control systems.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-341356